How to Calculate Block Wall Foundations

Determine the size of the building you are constructing. The width, height and footer requirements for your block wall foundation will depend on the type of structure you are building. For example, while a cosmetic retaining wall can be built up to 4 feet in height without structural support, anything higher than that will require rebar and special considerations for the footer.

Decide on the type of block you want to use in building the foundation. While some types of masonry blocks are sold with holes in the middle of the blocks, others are solid. The type of structure you are building will determine whether or not you need to use solid blocks. A simple shed in the back yard, for example, will have different block requirements than a three-story house.

Calculate the square footage for your materials. While you can measure for the blocks themselves fairly easily, you will need to use an online calculator or talk to a local specialist about how much sand, cement and rebar you will need to include in your project. The amount of mortar varies wildly depending on the size of the blocks, and, because not all foundations require rebar, you will need to factor that in, as well, on a case-by-case basis.

Factor in whether or not you can dig the foundation area by hand with a shovel or if you need to hire an excavating company to bring in heavy equipment to do the digging for you. While some projects, like backyard sheds, can be done by hand, house foundations will need to be dug out with a backhoe and excavating equipment; this requires specialists trained in the use of such machinery.